A. Field of the Invention
The present invention relates to methods and apparatus for visually assessing the vitality of biological tissue. More particularly, the invention relates to methods and apparatus for remote photogrammetric assessment of the extent of wound damage to external tissues of a human or animal.
B. Description of Background Art
Treatment of external wounds to the bodies of humans and animals usually includes visual evaluations of the healing process by a medical doctor, veterinarian, nurse or clinical specialist. Such evaluations are necessary to determine whether the wound treatment regimen is successful in reducing the volume or damage to necrotic tissue, indicating a satisfactory rate of healing of the wound.
The expertise of experienced doctors or clinicians in visually assessing changes in color, texture or area size of damaged biological tissue is an important asset in determining the effectiveness of medical procedures used to treat wounds. However, a problem exists in measuring the size of wounds, to determine whether the area of damaged biological tissue is increasing or decreasing. Such quantitative assessments are particularly important in monitoring the growth rate of wounds infected by gangrene or "flesh-eating" bacteria, since the rapid unchecked growth of these infections can necessitate amputation, or result in death.
A number of devices have been disclosed that relate generally to the field of assisting in visual evaluation of human body parts, some of which utilize optical means. These include the following U.S. Pat. Nos.:
Kawahara, 3,817,635, Jun. 18, 1974, Device For Measuring The Actual Dimension Of An Object At The Forward End Portion Of An Endoscope:
Discloses a device for measuring the actual dimension of an object in the field of view of an endoscope, the forward end portion of which is adapted to be inserted into a hollow portion of a living body or the like for the inspection thereof. The endoscope is provided with a fixed focal length objective lens system, a differential mechanism, and a sizing means along with adjusting means for the objective lens system, and a distance measuring means. One sizing means disclosed comprises a caliper having measured spaced pointers. A second sizing means disclosed comprises a pair of blades pivotally mounted in symmetrical relation to each other, the blades provided with cut out portions adapted for size measurement. A third sizing means disclosed comprises an iris diaphragm. The actual size of an object appearing in the field of view is measured directly by differentially coupling the differential mechanism with the sizing means and either the adjusting means for the objective lens system, or the distance measuring means for measuring the size of the object appearing in the field of view. An indicating means coupled with the differential mechanism indicates directly the actual dimension of the object regardless of the variation in the distance between the object and the forward end portion of the endoscope.
Mizumoto, 4,278,077, Jul. 14, 1981, Medical Camera System:
Discloses a capsule-shaped miniature camera comprising at least one permanent magnet, an induction coil, a lamp serially connected to the induction coil and a shutter device. The induction coil induces an electromotive force when a magnetic field generated by electromagnets outside the camera acts on it. The electromotive force turns on the lamp and drives the shutter device.
Landwehr, 4,370,039, Jan. 25, 1983, Method and Apparatus For Photographically Measuring An Object:
Discloses a method in which a composite photographic picture is generated through double-exposure, whereby the object, as for instance a person, is photographed on one half of the picture whereas a grid pattern is photographed on the other half; for the second exposure, person and grid pattern change position. In each instance of exposure, a line pattern is projected onto the object under utilization of one movable or two fixed, overhung projectors. Equipment is enclosed, permitting easy change of scenery.
Zoltan, 4,535,782, Aug. 20, 1985, Method For Determining Wound Volume:
Discloses a non-contacting volume determination method for use on wounds, in which a known pattern of lines optically projected onto the volume to be determined. The image of the projection viewed from an angle other than the projection, axis, along with the image of a reference volume located near the volume to be determined, are used to accurately determine the unknown volume.
Hallous, 4,564,295, Jan. 14, 1986, Apparatus And Method For Projection Moire Topography:
Discloses an apparatus and method for obtaining an improved moire fringe pattern image of an object. A beam of incoherent light is projected at the object. A grating is disposed in the path of the beam projected at the object, this grating being referred to as a projection grating. Means are provided for focusing the beam reflected from the object to obtain an image at an image plane. This movable grating is referred to as a reference grating. Means are provided for recording the image at the image plane, the recording means being, for example, a photographic or video camera. In accordance with an important feature of the invention, means are provided for moving the projection grating and the reference grating in synchronism. In a preferred embodiment, the projection and reference gratings are mounted in spaced relation in a movable member, and the synchronized motion of the gratings is implemented by moving the member. In a form of the disclosure, a double-projection set-up is used wherein two projection beams are directed at the object through first and second movable projection gratings, respectively. In this embodiment, the first and second projection gratings are moved in synchronism with the reference grating. This is preferably achieved by mounting the three gratings in appropriate spaced relationship in a common member, and moving the member.
Gormley, 4,569,358, Feb. 11, 1986, Optical Micrometry Of Skin Surfaces:
Discloses an apparatus and method for measuring changes in the topology of a skin surface in which a series of casts are taken of the skin surface, using an elastomeric material such as silicone rubber in a liquid state which is later polymerized, the casts being taken of a skin surface over a period of time and then measured by means of an automatically focusing microscope to produce a quantitative model of the changes in the topology of the surface.
Landwehr, 4,786,925, Nov. 22, 1988, Photographic Contour Measurement:
Discloses a method for measuring contours of a human body in which horizontal lines are projected onto a person from a plurality of overhead projectors, each projecting at a 45 degrees angle, all of the projectors have parallel optical axes, the person being photographed with the projected raster superimposed.
Steinhauer et al., 4,996,994, Mar. 5, 1991, Apparatus For Photogrammetrically Measuring The Human Head:
Discloses a process device for the photogrammetrical measurement of the human head, especially of the middle region of the face with the eye sockets, the nose, the cheek bones and the brows, which is comprised of a projector for projecting a pattern image onto the face and two cameras which can simultaneously take two pictures from two different directions of the face and head with the pattern image projected on it. The two cameras and the projector are supported by an apparatus carrier, which can be moved in a vertical direction relative to a base permanently connected in the device and in at least one horizontal direction. This minimum of one direction coincides with the optical axes of the cameras. The device will facilitate bringing both the projector and the cameras on the one hand and the human head on the other into the required relative position to one another as necessary to take the pictures.
Of the prior art references cited above, those most applicable to the problem of optically assessing external body parts include Landwehr, 4,370,039, which discloses a method and apparatus for measuring body contours that uses a projected grid pattern on the body, and a double photographic exposure, with the body in different positions for the two exposures, Zoltan, 4,535,782, which discloses a non-contacting volume determination method for use on wounds, in which a grid pattern is projected onto the wound, and the wound and pattern photographed, Hallous, 4,564,295, which discloses a method and apparatus for remotely measuring surface contours of an object that uses one or more grid patterns produced by projecting light through a grating onto the object surface, and a reference grating that produces a Moire pattern with light reflected off of the object, the patterns to be photographed, and Landwehr, 4,786,925, which discloses a method for remotely measuring body contours by projecting a grid pattern onto the body, and photographing the reflected pattern. Steinhauer et al. 4,996,994, discloses an apparatus for making photogrammetric measurements of the human head using two cameras photographing a grid pattern projected on the head.
None of the prior art references known to the present inventors is particularly well-suited to either qualitative or quantitative assessment of wound characteristics, because the projected grid patterns or Moire patterns used in prior art methods obscure certain wound features. Moreover, none of the prior art provides means for quantitatively establishing the color boundary of a wound. The present invention was conceived of to provide a method and apparatus for photogrammetric assessment of biological tissue that overcomes limitations of the prior art.